According to internal Ubisoft estimates, Assassin's Creed II has sold 1.6 million units in the first week of release, 32% more than the original Assassin's Creed sold two years ago.

While Assassin's Creed the first remains the fastest selling new video game IP in U.S. history, it's younger brother isn't doing too shabby itself, selling more, reviewing higher, and generally making Altair look like a chump.

According to Mr. Totilo's review of the game as well as my own extensive experience with AC2, I'd say the faster sales are due to a combination of brand recognition and the fact that Assassin's Creed II is at least 32% better than the original.